This invention relates in general to vehicle power steering systems and in particular to a torque sensor assembly for use in such a vehicle power steering system.
Automotive vehicles typically include a power steering system to assist in turning steerable wheels of the vehicle. The power steering system will typically include a rack and pinion assembly to convert rotational movement of a steering wheel of the vehicle into linear movement to effect turning of the steerable wheels. A torque sensor assembly is commonly used to measure a direction and magnitude of steering torque applied to the steering wheel by a driver of the vehicle. The measured direction and magnitude of the steering torque is then used by an electronic control unit to operate a power source that assists in turning the steerable wheels.
The torque sensor assembly may operate by using a magnetic sensor to detect variations in a magnetic field generated by a magnet fixed to a steering component that rotates with the steering wheel. However, such a torque sensor assembly is susceptible to external magnetic fields that may cause an output of the torque sensor to misrepresent the steering torque applied by the driver. The external magnetic fields may be produced by a source external to the vehicle and/or from within the vehicle. For example, the external magnetic fields may result from high current electrical cables—e.g., a starter cable—being routed adjacent the torque sensor assembly due to packaging requirements for the vehicle. Furthermore, autonomous vehicles are expected to require steering systems with increasingly precise torque sensor assemblies that are not susceptible to external magnetic fields.
The torque sensor assembly may be shielded from the external magnetic fields to prevent misrepresentation of the steering torque applied by the driver. However, such shielding adds cost, weight, and complexity to the vehicle. Thus it would be desirable to have a torque sensor assembly that mitigates external magnetic fields without requiring shielding.